Detecting Spin Currents in Superconductors by Doppler-shifted Spin-polarized Photoemission*

A method is proposed to detect high-velocity spin currents by exploiting the Doppler effect to energetically separate photoelectrons of opposite spin polarizations. We predict that a highly polarized photocurrent will emit from the edge of the valence band. For spin currents that are predicted to exist in superconductors by the Spin Meissner effect, the expected Doppler-induced energy separation is measurable with current experimental resolutions.